Spring for ratchet mechanisms



Patented Sept. 10, 1935 UNITED STATES PATENT OFFICE Application May 9, 1932, Serial No. 610,102

1 Claim.

This invention relates broadly to ratchet mechanism but more specifically to improvements in the springs associated with the ratchet mechanism used in connection with rock drills.

In constructing a ratchet mechanism for rock drills; it is the common practice to provide a ried bar having a head within which is drilled a plurality of restricted bores. Co-operating with this rifled bar, there is a ratchet ring which is connected thereto by a plurality of pawls actuated by a spring pressed plunger longitudinally movable within the restricted bores. Heretofore, the springs were wound substantially cylindrical with an outside diameter somewhat smaller than the diameter of the bore, permitting thereby the frictional engagement of its coil with the inner peripheral wall of the bore. Due to the rapid compression and expansion of the spring, the coils thereof, rubbing against the inner wall of the bore, would prematurely wear and cause the breakage of the spring, increasing thereby the cost of operation.

It is among the objects of this invention to provide a ratchet mechanism for rock drills with the spring having the coils subjected to mechanical stress, being free of frictional engagement with the inner peripheral wall of the bore within which the spring is mounted, preventing thereby a premature wear and breakage of the spring as well as reducing the cost of operation.

Other objects more or less ancillary to the foregoing and the manner in which the above mentioned object is realized, will appear in the following description, which considered in connection with the accompanying drawing, sets forth the preferred embodiment of the invention.

In the drawing:

Fig. 1 is a longitudinal view, partly in section, of a rock drill representative of one of the types of machines in winch the ratchet mechanism may be incorporated.

Fig. 2 is an enlarged cross sectional view taken in a plane indicated by line 2--2 in Fig. l, illustratlng the ratchet mechanism with the springs incorporated therewith.

Fig. 3 is an enlarged longitudinal view of the spring.

The embodiment herein chosen to illustrate the present invention is a rock drill of the hammer type which comprises a cylinder Ill within which there is mounted a piston I I formed with an extended stem portion or hammer I2, adapted to co-operate with the head of a cutting tool I3 in the manner customarily employed in percussive rock drills. Mounted within the rearward end of the cylinder, there is a valve block Il having a valve I5 reciprocable therein for controlling the admission of motive fluid within the cylinder I0 to actuate the piston Il. The Valve block I4 is maintained within the cylinder I0 by the co-operation of a back head I6 which is secured by a pair of side bolts (not shown). During the drilling operation, i. e. when the hammer I2 is delivering its blows to the cutting tool I3, it is necessary to rotate the cutting tool. 10 For this purpose there is provided a rotation mechanism, comprising a rie bar or stem I'I which is slidably cngageable within the head of the piston II in a bore of complemental conguration. The rifled stem Il is provided with an enlarged head I8 within which there is drilled a plurality of restricted bores I9. Within each of said bores there is reciprocably disposed a plunger subjected to the action of a compression spring 2l disposed rearwardly thereof. Toward its ends, 20 the spring is manufactured with enlarged coils of an outside diameter substantially equal to the diameter of the bore I9, and capable of engagement with the inner peripheral wall of the bore I9, for guiding the spring in axial alignment with the plunger 20. These last coils are closed in upon each other as shown at 22 for the purpose which will be explained later. Pivotally secured within the enlarged head I8, there is a plurality of pawls 23 upon which the spring pressed 30 plungers 20 are acting to maintain the free end thereof away from the enlarged head I8. This head and its appurtenances is encompassed within a ring 24, having its inner peripheral wall provided with a plurality of longitudinally disposed teeth 25 with which the free ends of the pawls 23 are `capable of intermittent engagement. y

During the forward stroke of the piston II, the rifled bar I1, by reason of its engagement with the piston II, is made to rotate in one direction. During this motion, the free end of the pawls 23 in engagement with the plunger 20, Will pass over the teeth 25 and will cause a rapid compression and expansion of the springs 2I. The working coils of the spring, i. e. the coils intermediate the enlarged coils thereof, being of an outside diameter smaller than the internalA diameter of the bores I9, are free from frictional engagement with the inner peripheral wall of the bore I9 and consequently are not subjected 50 to wear. 'I'he enlarged coils in engagement with the inner peripheral wall of the bore I9 to guide the spring in axial alignment therewith, are closed in upon each other to prevent the compression or expansion thereof. These enlarged 55 coils are subjected to wear but are free of mechanical stress, preventing thereby the combination of wear and mechanical stress resulting in the breakage oi the coils.

Although the foregoing description is necessarily of a. detailed character in order to completely set forth the invention, it is to be understood that the specific terminology is not intended to be restrictive or coniining and it is to be further understood that various rearrangements of parts and modication of structural detail may be resorted to without departing from the scope or spirit of the invention as herein claimed.

I claim:

Y :A helical compression spring Vformed of compressible and non-compressible coils, said noncompressible coils constituting the ends of said spring, the diameter of said last coils being substantially equal to that of a bore within which said spring may be disposed, permitting thereby the engagement of said last coils with the inner wall of said bore so as to center said spring therein, the diameter of each ef said compressible coils being substantially equal but smaller than that of said non-compressible coils, thus causing an equal deection of the compressible coils when a load is applied to the spring and preventing the possible engagement of said compressible coils with the inner wall of said bore.

LED L. RICHARDSON.V Y Y 

